Merge pull request ethereum#2093 from ethereum/eth1data-params

double eth1data params

Merge pull request ethereum#2057 from ethereum/dev

release v0.12.3

Merge pull request ethereum#1955 from ethereum/dev

release v0.12.2

Merge pull request ethereum#1868 from ethereum/dev

Release v0.12.1

Merge pull request ethereum#1829 from ethereum/dev

release v0.12.0

Merge pull request ethereum#1818 from ethereum/v011x

v0.11 multiple blocks in single slot patch

Merge pull request ethereum#1753 from ethereum/gen-req-fix

fix requirements.txt for bls generator

Merge pull request ethereum#1686 from ethereum/v011x

Release `v0.11.1` to master

Merge pull request ethereum#1686 from ethereum/v011x

Release `v0.11.1` to master

Merge pull request ethereum#1645 from ethereum/dev

Release v0.11.0 into master